Branches, Bifurcations and Retroflections over the Tail of the Grand Banks

大浅滩尾部的分支、分叉和反射

• 批准号: 0550423
• 负责人: Michael McCartney
• 金额: $ 49.99万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-05-01 至 2009-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0550423&HistoricalAwards=false
• 关键词: Branches; Bifurcations; Retroflections; over; Tail

It is proposed to analyze existing data (hydrography, current meter, surface drifter, subsurface float, altimetric and SST observations), to characterize the mean and variable (mesoscale through seasonal to interannual) regional circulation around the Tail of the Grand Banks, ultimately enabling a more complete description of the branches, bifurcations and retroflections of the currents.This is a critical location for the North Atlantic circulation. There, major branches of the wind-driven (Gulf Stream and Labrador Current) and thermohaline circulations (Deep Western Boundary Current) meet, and dramatic changes in the character and pathways of the currents follow. The Labrador Current and Deep Western Boundary Current partially retroflect near the Tail of the Banks, but the amount of transport lost by the combined currents and the details of the retroflection pathway are unknown. Similarly, south of the Grand Banks, the Gulf Stream approaches the Tail from the west with full-depth flow carrying large transport. At the Tail, the Gulf Stream splits into four branches, with a critical branch turning north across the Tail to feed the North Atlantic Current east of the Grand Banks. The exact partitioning of transport into separate branches remains unknown. The interaction between the deep-reaching currents appears forced and constrained by the shoaling topography of the Tail, resulting in a regional distortion of the thermocline into a cyclonic meander over the Tail a trough - remarkably stable in both space and time. Based on existing observations we hypothesize that the trough configuration represents a bottleneck for the approaching currents, limiting the strengths of the current branches crossing the Tail. This will be a quantitative description within the limits of existing data, and may point to critical new measurements that would tighten the constraints on the characterization. The output from high-resolution numerical models will also be examined with the goal of gaining insight into the dynamics of the Tail-induced bottleneck.

建议分析现有资料（水文、海流计、地表漂流、地下浮子、高度计和海温观测），以表征大浅滩尾部周围的平均和可变（从季节到年际的中尺度）区域环流，最终能够更完整地描述洋流的分支、分岔和反射。这是北大西洋环流的关键位置。在那里，风力驱动的主要分支（墨西哥湾流和拉布拉多流）和热盐环流（深西部边界流）相遇，洋流的特征和路径随之发生巨大变化。拉布拉多海流和深西部边界海流在靠近河岸尾部的地方进行部分反射，但是由于这两股洋流的结合而损失的运输量和反射路径的细节都是未知的。同样，在大浅滩以南，墨西哥湾流从西向尾部靠近，带着大量运输的全深度流。在尾部，墨西哥湾流分成四个分支，其中一个关键分支向北穿过尾部，流入大浅滩以东的北大西洋洋流。运输的确切划分仍然是未知的。深流之间的相互作用似乎受到尾部浅滩地形的强迫和限制，导致温跃层的区域扭曲成为尾部槽的气旋蜿蜒-在空间和时间上都非常稳定。根据现有的观察，我们假设槽结构代表了接近电流的瓶颈，限制了电流分支穿过尾部的强度。这将是在现有数据限制内的定量描述，并可能指出关键的新测量，将收紧表征的限制。高分辨率数值模型的输出也将被检查，目的是深入了解尾部引起的瓶颈的动力学。